1. Field of the Invention
This invention relates to an implanting stent useful in the treatment of any stricture in a body passageway such as blood vessel, bile duct, trachea, esophagus, and ureter.
2. Prior Art
Stents are generally tubular shaped devices which function to maintain open a segment of a blood vessel or other anatomical lumen. They are useful in the treatment of stenosis in blood vessels or other narrowed passageways.
In terms of their function and implantation, stents are generally classified into self-expandable stents and balloon expandable stents. The balloon expandable stent which itself has no expanding function is secured at a desired intralumenal location by mounting the stent on a balloon, delivering the stent to the desired location, and inflating the balloon so that the stent is expanded through plastic deformation by the dilating force of the balloon until it comes in close contact with the inner surface of the desired location. Stents of this type require the operation of expanding the stent as mentioned above.
With respect to balloon expandable stents, reference is made to Palmaz, U.S. Pat. Nos. 4,733,665 and 4,776,337 and Schatz, U.S. Pat. No. 5,195,984, which are incorporated herein by reference. These stents are pipes having axial slots formed therein. The slots are arranged such that they may take interconnected rhombus shapes when the stent is expanded.
The expandable intralumenal graft or stent of U.S. Pat Nos. 4,733,665 and 4,776,337 is improved in shape retention after expansion because slots take interconnected rhombus shapes. That is, the stent is resistant to the contracting force of a blood vessel. Another advantage is that when it is desired to partially enlarge the expanded diameter, an additional balloon corresponding to the enlarged diameter may be inserted inside the stent. Since the stent in an unexpanded state is a pipe having axial slots formed therein as viewed in side elevation, the stent lacks flexibility in an axial direction so that when the stent is to be inserted to the lesion, it is sometimes difficult to deliver the stent along a winding blood vessel. Additionally, when expanded, the stent is substantially reduced in overall length, leaving possibilities that the stenosis in a blood vessel is not dilated over its entirety and that the actual position of the stent is offset from the intended location under radiographic observation. In either case, effective treatment of stenosis is not expectable.